speaker has double plugs, goes to main and daughterboard, SPEAKER SWITCH P3 on main board, and speaker on corner of daughter board.

Below is a picture from Ted showing the later style electronics, specifically the fan driven smoke units. Note there is one "smoke power supply" board shown, this powers one smoke unit. The regulators and "smarts" for the other smoke unit are on the main board on the chassis.

In the composite picture below, you can see the second "smoke power supply" on the chassis, to the left of the "main board"